Water-based fluids such as, for example, drilling fluids, milling fluids, mining fluids, water-based metal working fluids, food additives and water-based paints, are useful in a variety of industrial applications. It is well known to those skilled in the art of drilling wells to tap subterranean deposits of natural resources, such as gas, geothermal steam or oil, especially when drilling by the rotary method or the percussion method wherein cuttings must be removed from the bore hole, it is necessary to use a drilling fluid.
The use of water-based fluids in, for example, workover and completion fluids in oil field operations is also well known to those skilled in the art. Workover fluids are those fluids used during remedial work in a drilled well. Such remedial work includes removing tubing, replacing a pump, cleaning out sand or other deposits, logging, etc. Workover also broadly includes steps used in preparing an existing well for secondary or tertiary recovery such as polymer addition, micellar flooding, steam injection, etc.
Completion fluids are those fluids used during drilling and during the steps of completion, or recompletion, of the well. Completion operation can include perforating the casing, setting the tubing and pump, etc. Both workover and completion fluids are used in part to control well pressure, to stop the well from blowing out while it is being completed or worked over, or to prevent the collapse of casing from over pressure.
Salts of sulfonated asphalt and their blends with materials such as, for example, gilsonite, blown asphalt, lignite, and mixtures thereof are commonly used as additives in drilling fluids. These additives, however, cause some foaming in water or water-based fluids. Furthermore, these additives are only partially soluble in the fluids. Their solubility in the fluids depends on factors such as salt content, solids content, pH, and combinations thereof. Therefore, a significant amount of the undissolved additives can be screened out with drilled solids by solid control equipment. This leads to problems, when using these additives in water-based drilling fluids, such as, for example, plugging of shale shaker screen, poor performance of the additives, and combinations thereof.
Liquid additives and processes therefore have been developed to overcome some of the problems associated with using dry additives. Processes have also been developed for formulating the liquid additives. For example, U.S. Pat. No. 5,114,597 discloses a process for manufacturing a water-based drilling fluid wherein the process comprises mixing a hydrophobic carbon black and either a surfactant or a dispersant followed by shearing the resulting mixture to convert the hydrophobic carbon black to hydrophilic carbon black. However, a usable liquid additive of neutralized asphalt sulfonate or a blend that contains neutralized asphalt sulfonate as a component cannot be prepared by the process disclosed in the '597 patent because the additive becomes too viscous or solids settle out at the bottom of the additive. Although U.S. Pat. No. 5,091,448 provides an excellent process for preparing a very stable liquid additive suspension, the liquid additive which contains a hydrocarbon as a liquid carrier cannot be used in some areas where environmental regulations are of concern. It is therefore highly desirable to develop a process that prepares a stable liquid additive suspension which is environmentally acceptable.